A diffusable factor in Scottish coagulation factor concentrates can inhibit lymphocyte transformation in vitro.

Coagulation factor VIII and IX concentrates produced in Scotland inhibited human lymphocyte transformation induced by lectins or the recall antigen, purified protein derivative of tuberculin (PPD). Although concanavalin A could bind factor VIII directly and PHA could bind factor IX directly, most of the inhibition was not due to direct clotting factor - lectin interaction nor to simple toxicity. Most of the inhibitory activity from both clotting factors could be removed by dialysis. A similar degree of inhibition was observed when the buffers used to prepare the concentrates were substituted for the concentrates themselves, and a comparable concentration of sodium citrate was also found to be inhibitory. Coagulation factor VIII partially purified by gel filtration was not found to have an appreciable effect on lymphocyte transformation in vitro.